For whatever reason, CV processors are seldom included in people's systems. It's funny, because they are cheap and easy to design/build. This is something that Buchla, Serge, and Ken have always understood to be very useful - people are slowly coming around. Basics to have?:

Between combinations of these, one can get really creative with voltages. And they each only need an op amp or two, which makes them easy enough for me to do on perfboard. I started by copying the schematics from Barry Klein's book, (which are mostly from Electronotes) and slowly trying to understand what was happening there.

Klein's book also opened my eyes to nonlinear waveshaping, which ultimately offers more timbral possibilities than subtractive filters while using cheaper parts and being easier to build. Since I had this stuff on the brain, I was psyched to check out Ken's VCO!

Oh, and this morning, before I went to bed - I just finished my two VCOs finally! They've got their styrene caps, trimpots, and tempcos. Now I just need to get my bench clean enough to test them, so the wire clippings and parts don't blow them up.

anyway, so i didnt bother trying it for 3 octaves yet, i wanted to check what it was like, so i reconnected my tune pots and found that the range of the course pot was completely fuxed. The whole audio range was located in a degree or 2 of the pot. So this is obviously wrong.

This is the response that I'm getting also after wiring up the tune pot on this CGS VCO. Were you able to solve this problem?

i got a bit excited and had made lots of panels and just fitted them with any pots i could find to see if everything fit, i forgot about this and assumed that the components were all correct. on top of that i got a bit lost with my panel wiring. i started fresh, puled everything out, examined the page again and re-wired it up. tuning went without a hitch

For +/- 15V operation, you may prefer to replace the 330k/240k sawtooth bias resistors with 600k/200k as per the ASM-1

Anyone done this? I'm in the middle of building my 2 CGS48s and I'm going for this option..

Or is it better to do the 220K/240K with AC couple output?
But then I need an DC output aswell.. which might be good. Since I'm gonna build a CGS38 saw pitch shifter that needs a saw that goes from 0 to +5V. (Or is the DC output 0 to 10V?)

Mine seems to be between 0.5V - 5.5V? (I haven't got the best oscilloscope in the world, but it seems like the DC offset is kinda high..).

Any ways to trim it down? Should I change the 220K resistor in the 330K/220K configuration to something else?

And my "sine" like shape looks really more like then "sine". Anyone got a photo of theirs?

Edit -

So I've been playing around with different resistor values.

300K instead of 240K gave quite a good result. The DC saw seems to be just a tad over 0V. Hard for me to actually measure. But it's not much. It looks and "feels" good! I haven't listened to it, so I don't know. I'm doing all this, because I wanted to use it as a modulation source for other stuff..

And as the sine part of the circuit. I was to stupid to undestand that I was supposed to wait for a few second while turning the trim pot, to let it all settle! So now the sine looks good aswell

Can anyone post a wiring diagram (similar to the one's that Ken posts on some of his other module's pages) for the VCO with every option implemented? It would be a great asset to all of us that are getting ready to build this great VCO!

I'll post audio and video as soon as I'm done with mine. Just need to add a TL074 + parts to the sine and TSO output, so they're 5Vpp. Cause right now they're to low to be usefull.

Though I have to say, modulate the TSO in audio rate and you get very nice timbres...

The wiring isn't that hard to do. I think it's all in the schematics. Except for the PWM. But wire a pot with +15V on one leg and -15V on the other, then put a 330K resistor between the pot and the PW pad and you can change between 10% to 90% pulsewidth._________________http://www.thehumancomparator.net/

does the pulsewidth remain at 10-90% range at any frequency? I've noticed in some PW designs the width can change with the frequency or cut out completely._________________Youtube!modular demos!Whacky tunes!

I've breadboarded that comparator section and a few others using a +/-5V saw with that kind of result. My vco was different but I don't think it would have mattered unless the cgs vco levels differ._________________Youtube!modular demos!Whacky tunes!

I haven't tested it yet though. But it's just 2 inverting amplifiers after each other, and the second op amp has a feedback resistor that is twice the size of the input resistor - which should cause a gain of 2?_________________http://www.thehumancomparator.net/

I checked yesterday, and the higher the tune pot, the lower the output. I'll hook up my frequency counter to it and see aprox where it starts to go down._________________http://www.thehumancomparator.net/

Correct me if this is wrong, I think these are based on the functionality of the CV inputs on the circa '73 Serge VCO. (Ken's design is different though.

I can tell you ,these vco's are everything except close to the serge one.

Ken replaced his '73 VCOs with these, the only similarity is some of the panels controls. It does not work, feel, or sound anything like the original Serge "Oscillator". The original '73 circuit is extremely clever, and fun, but Ken wanted something which could actually track for more than a single octave or so.

Look up Osamu Hoshuyama's schematic of the 1973 Oscillator, and compare with the diagram for Ken's CGS48 VCO. They are very different.

Correct me if this is wrong, I think these are based on the functionality of the CV inputs on the circa '73 Serge VCO. (Ken's design is different though.

I can tell you ,these vco's are everything except close to the serge one.

Ken replaced his '73 VCOs with these, the only similarity is some of the panels controls. It does not work, feel, or sound anything like the original Serge "Oscillator". The original '73 circuit is extremely clever, and fun, but Ken wanted something which could actually track for more than a single octave or so.

Look up Osamu Hoshuyama's schematic of the 1973 Oscillator, and compare with the diagram for Ken's CGS48 VCO. They are very different.

i have a serge and cgs vco at home,but i like the cgs pcb because of its dencity and amounth of components,I did buy plenty of them 18 but i still not build 6 of them finished pcb's onto panels,i wander if its worth it as i have redrawn the PCO and have pcb layout ready and read recently the troubles ppl have with it (not v/oct on 5 oct despite the expensive matched transistor pair,low outputs,and what i can expect more?..)

I think the problem with the low output is a limitation from the LM3900? Since it's only single sided...?

I think the CGS VCO is great. I haven't calibrated mine, but I generally see no use in trying to get as much tracking as possible out of my VCOs..
Modulating the waveshaper in audio rate is great fun!_________________http://www.thehumancomparator.net/

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